Air suspensions include numerous air springs and shock absorbers that are used to improve vehicle ride characteristics by accommodating variations in road surfaces. Air suspensions are common in high load capacity applications, such as heavy-duty line haul applications for example, where cargo loads can vary significantly. Significant load variations can adversely affect ride quality.
Various attempts have been made to provide a variable suspension response by modifying performance of the shock absorbers or air springs depending on vehicle or road conditions. Ride control and height control systems have traditionally been used to provide a variable suspension response. Some ride control systems provide various degrees of damping and spring rate adjustment to compensate for loaded and empty vehicle conditions. Height control systems monitor and control air spring pressures to maintain a desired ride height. These height control systems actively adjust ride height by supplying or releasing air from the air springs.
With either the ride control or height control systems, air is cycled into and out of the air springs. This cycle of varying air spring pressure has often been utilized to activate a shock absorber adjusting device, to further compensate for ride quality variation by adjusting shock absorber damping. Current adjustment systems utilize a hollow rod that is coupled to a piston received within the shock absorber. An internal valve assembly is positioned within the hollow rod adjacent to the piston. An air pressure signal is communicated from the air springs to an internal valve assembly through the hollow rod to adjust damping or lock movement of the shock absorber.
The internal valve assembly defines an effective area on which the air pressure signal can act. Due to the position of the internal valve assembly within the hollow rod, this effective area is relatively small. This means that the force acting on the internal valve assembly is not always adequate to overcome valve seal friction and often cannot hold a desired valve setting. Thus, there is a need for a pneumatic actuator for a shock absorber adjustment mechanism that can more effectively and efficiently control damping adjustment, as well as overcoming the other above-mentioned deficiencies in the prior art.